This invention relates to the liquefaction of acetylene streams containing water by selective hydration and/or condensation in the presence of an alumina-zirconia catalyst. In particular, it concerns the hydration and/or condensation of acetylene and acetylenic compounds to aliphatic, aromatic and oxygenated compounds. These compounds are useful directly, or upon hydrogenation, as fuel additives to increase octane of motor fuel. It also concerns a process wherein presence of water in the crude stream results in lessened coke build-up on the catalyst, thus increasing catalyst life.
Acetylene and acetylenic compounds are produced by known technology from methane. Methane is cheap and abundant. Much of it occurs where no pipeline facilities exist, and it cannot be transported readily. However, methane can be converted to impure acetylene by partial combustion in the presence of air and by direct pyrolysis. A typical output stream from a methane oxidation plant producing a crude acetylene stream can be characterized as containing methane, carbon dioxide, oxygen, nitrogen, water, hydrogen, carbon monoxide, acetylene and acetylenic compounds. In cases where a higher hydrocarbon than methane is used as feedstock, the output stream also contains olefins such as ethylene, propylene, butadiene; aromatics such as benzene and naphthalene and miscellaneous higher hydrocarbons. Significant amounts of carbon black and tars are also produced.
Accordingly, a typical output stream from a methane pyrolysis plant contains acetylene, hydrogen, methane, ethylene, carbon monoxide, carbon dioxide, nitrogen and higher acetylenes (Ency. Chem. Tech., 3rd, 1, 226).
The isolation of acetylene for further processing presents a complicated problem. The unstable, exploxive nature of acetylene has required certain restrictions on use of separation systems utilized for other hydrocarbon systems. These restrictions indicate that partial pressure of acetylene should not exceed 15-30 psig to avoid possible decomposition and detonation. Similar limitations have been developed as to operating temperatures which should not be below 95.degree.-105.degree. C. Low temperatures can lead to the formation of liquid or solid acetylene or its homologs with attendant danger of decomposition. Because of these problems, processing and recovery of acetylene from a hydrocarbon oxidation process has typically been by absorption-desorption techniques using one or more selective solvents.
It has been unexpectedly found that a crude acetylene stream containing water can be processed over a zirconia-alumina catalyst without prior purification at temperatures of from about 200.degree. C. to about 500.degree. C. at atmospheric pressure to produce aromatic hydrocarbons, or aromatic hydrocarbons and aliphatic hydrocarbons or oxygenated compounds, depending upon the ratios of acetylene and water present. Other compounds normally present in the output of a crude acetylene process such as carbon dioxide, nitrogen, carbon monoxide, hydrogen and oxygen can also be present in the crude acetylene stream. The product mix of the hydration reaction can be utilized directly as motor fuel additives to improve octane or can be hydrogenated to obtain saturated compounds also suitable for use as motor fuel additives to improve octane. The presence of water also increases catalyst life by controlling the rate of coke build-up upon the catalyst.
It has long been known that pure acetylene can be copolymerized to benzene, styrene and higher aromatics. For example, U.S. Pat. No. 2,723,299 teaches the preparation of benzene and styrene from acetylene and vinylacetylene in a solvent with a catalyst, (triphenyl-phosphine) nickel dicarbonyl and a cocatalyst, copper ammonium halides. Dibenzylideneacetone-palladium(O) and platinum(O) complexes (Chem. Communications (1971), 1604), and cyclobutadiene-palladium halide complexes (J. Organometal. Chem., 26, 407 (1971)) have been used for cyclotrimerizing acetylene and substituted acetylenes. U.S. Pat. No. 3,365,510 teaches the preparation of high purity benzene from acetylene by trimerization over a catalyst of activated alumina of surface area of 30 to 400 m.sup.2 /g containing an oxide of V.sub.2 O.sub.5, Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, CrO.sub.3, MoO.sub.3, WO.sub.3 or Mo.sub.2 O.sub.5 in Group VB or VIB of the Periodic Table. U.S. Pat. No. 4,009,219 teaches the liquefaction of acetylene to aromatic hydrocarbons comprising principally benzene and alkylbenzenes by cyclotrimerization in the presence of a catalyst consisting of silica-alumina containing an oxide of chromium or vanadium in the strict absence of moisture in both the catalyst and the reacting acetylene.
Other previous teachings relate to processes for converting acetylenic hydrocarbons to aromatic hydrocarbons. For example, U.S. Pat. No. 2,217,009 teaches the conversion of 1-alkynes having 6 or more carbon atoms in straight chain arrangement at temperatures within the range of 450.degree.-700.degree. C., and contact times of 0.1 to 30 seconds with catalysts comprising a metal selected from the group consisting of titanium, zirconium, cerium, hafnium and thorium. Example III of U.S. Pat. No. 2,217,009 teaches zirconium dioxide on alumina catalyzes the production of benzene from hexyne-1. British Pat. No. 473,219 teaches preparation of monovinylacetylene, benzene, toluene, styrene and other aromatic compounds from acetylene in the presence of a catalyst containing a metal selected from the group consisting of metallic gold, molybdenum, silver and their alloys, also alloys containing iron, alumina, silicon and chromium, as well as oxides of titanium, zirconium and uranium. U.S. Pat. No. 2,819,325 teaches that liquid aromatic hydrocarbons comprising principally benzene and alkylbenzenes are obtained by the polymerization of 1-alkynes using a chromium oxide-containing catalyst comprising a catalyst support which is at least one member selected from the group consisting of silica, alumina, zirconia, titania, and siliceous natural clays over a wide range of temperature and pressure.
It has long been known that metals of Group IIB of the Periodic Table, as separate compounds or in the presence of alumina, are useful in preparing unsaturated compounds from acetylene. For example, U.S. Pat. No. 2,716,142 teaches the preparation of vinyl fluoride by reacting acetylene with hydrogen fluoride in the presence of a catalyst comprising particles of a zinc compound of the class consisting of zinc oxide, zinc nitrate and zinc sulfide. U.S. Pat. No. 2,634,300 teaches preparation of unsaturated monofluorides by reacting hydrogen fluoride with acetylenic hydrocarbons in the presence of a catalyst comprising alumina or aluminum fluoride, or alumina combined with other metals such as aluminum, antimony, cobalt, cadmium and zinc. U.S. Pat. No. 2,574,480 teaches the hydrofluorination of acetylene hydrocarbons in the presence of hydrogen fluoride and a catalyst comprising from 70 to 95 weight percent alumina and from 5 to 30 weight percent zinc fluoride. U.S. Pat. No. 3,413,361 teaches a process for production of vinyl fluoride from acetylene and hydrogen fluoride over a cadmium salt catalyst such as cadmium sulfate, cadmium nitrate, cadmium acetate or a mixture thereof.
Gas streams containing acetylenes and diolefins have been purified by selective hydrogenation of acetylenes using Group VIII metal catalysts. Typical hydrogenation processes are taught in U.S. Pat. Nos. 3,420,618 and 3,489,809, which are incorporated by reference.
It is also known that the condensation of acetylene and acetylenic compounds in the presence of water is often deleterious to the catalyst and to the catalytic reaction. For example, it is known that (triphenylphosphine) nickel dicarbonyl, as well as dibenzylideneacetone palladium complexes and alkyl palladium halide complexes, decompose in the presence of water. Strong Lewis acid catalysts such as those taught by U.S. Pat. No. 3,365,510 and U.S. Pat. No. 4,009,219 are also deactivated by the presence of water which is a Lewis base. U.S. Pat. No. 3,365,510 teaches that the synthesis of benzene from acetylene in the presence of Lewis acid catalysts is increased by thorough drying of the catalyst. U.S. Pat. No. 4,009,219 teaches that thorough drying of both the acetylene stream and the catalysts are very important to insure good yields and a low rate of catalyst deactivation. Accordingly, condensation of acetylene and acetylenic compounds is typically in an anhydrous environment, often in an organic solvent.
Acetaldehyde has long been produced by the addition of water to acetylene (S. A. Miller, "Acetylene" Vol. 2, Ernest Benn Limited, London, 1966; p 141-144). Commercially, aqueous mercuric sulfate solutions have been used to catalyze this reaction. The number of commercial vapor phase hydration processes is rather small. However, the catalyzed addition of water to acetylene by zinc compounds in the vapor phase was practiced in Germany during World War II (Miller, p. 146). The acetylene was saturated with water at 80.degree. C., heated to 350.degree. C. and passed through beds of zinc oxide. The principal product was acetone, about 60 carbon % yield, along with acetaldehyde and high ketones. Under comparable conditions, the instant process provides higher acetylene conversions and better organic liquid selectivities than available with zinc oxide based catalysts. The instant process in the presence of an alumina-zirconia catalyst not only tolerates the presence of water but results in the hydration and condensation of acetylene and acetylenic compounds to oxygenated compounds as well as condensation of acetylene and acetylenic compounds to aliphatic and aromatic compounds. The presence of water in the feed stream in the instant process is beneficial in that coke build-up on the catalyst is controlled.
Accordingly, a process has not been previously known for liquefaction of acetylene and acetylenic compounds in a crude acetylene stream containing water in the presence of a zirconia-alumina catalyst, to produce aliphatic, aromatic and oxygenated compounds at atmospheric pressure and temperatures within the range of from 200.degree. C. to about 500.degree. C.